Magnetic pallet for anchorage of ferromagnetic parts for machining by machine tools with horizontal tool axis

ABSTRACT

A magnetic pallet ( 1 ) for anchorage of a ferromagnetic part to be taken for machining to a machine tool with horizontal tool axis, said magnetic pallet ( 1 ) comprising a base plate ( 3 ), a vertical parallelepiped shoulder ( 5 ) extending from the base plate ( 3 ), a first plurality of magnetic conductors ( 15 ) arranged in a matrix and which can be polarised magnetically so as to define a first surface for vertical magnetic anchorage of ferrous parts at a first lateral face ( 4 ) of said shoulder ( 5 ), characterised in that said base plate ( 3 ) and said shoulder ( 5 ) are formed from a single ferromagnetic monolithic block, and in that from said ferromagnetic monolithic block, at said first lateral face ( 4 ) of said shoulder ( 5 ), a first recess ( 7 ) is formed for housing said first plurality of magnetic conductors ( 15 ).

[0001] The present invention relates to a magnetic pallet for theanchorage of a ferrous part to be machined by a machine tool withhorizontal tool axis.

[0002] This magnetic pallet comprises notoriously a base plate driven totraverse the bed of the machine tool to bring the part to be machinedinto the work area and to remove the machined part from the work area,and a vertical parallelepiped shoulder attached to the base plate and atleast one vertical magnetic surface which can be polarised to achieveanchorage of the part.

[0003] Each magnetic anchorage surface with which the pallet is providedis composed of a plurality of magnetic conductors arranged in a matrixand each one is supplied by a corresponding permanent and reversiblemagnet encircled by an electric induction coil capable of changing thedirection of polarisation of the permanent magnet so as to commutate themagnetic surface from the activated condition to the de-activated oneand vice versa.

[0004] The magnetic surface is surrounded and protected by aferromagnetic crown which is part of the magnetic circuit generated bythe permanent reversible magnets both in the activated condition and inthe de-activated condition of the magnetic surface.

[0005] The ferromagnetic crown, inside of which the magnetic conductorsare placed with the relative permanent reversible magnets and, ifnecessary, with other secondary permanent magnets also supplying themagnetic conductors, is placed on a corresponding lateral face of theshoulder of the magnetic pallet.

[0006] The magnetic pallet has to have structural rigidity and stabilityso as to guarantee that machining of the part can be performed whilemaintaining extreme machining precision.

[0007] Nevertheless, for example when machining of the part moves to theapex portion of the magnetic pallet, the action of the tool on the partmay cause slight yields or temporary deformation of the structure of themagnetic pallet and the movement induced in this way of the relativeposition between the workpiece and tool may jeopardise machiningprecision.

[0008] Clearly the slight structural yields which may occur inside thestructure of the pallet mainly originate at the areas of joining, formedby welding or by means of tightening screws, or another known manner,between the base plate and the shoulder, and between the shoulder andthe ferromagnetic crown placed on the shoulder.

[0009] The object of the present invention is therefore that ofproviding a magnetic pallet and a method for the production of amagnetic pallet for anchorage of a ferrous part to be machined by amachine tool with horizontal tool axis, which magnetic pallet hasintrinsic stability and rigidity such as to allow extremely precise andthorough machining of the part.

[0010] Another object of the present invention is that of providing amagnetic pallet and a method for production of a magnetic pallet whichare inexpensive.

[0011] These objects are achieved by a magnetic pallet in accordancewith claim 1 and by a method of producing a magnetic pallet inaccordance with claim 5.

[0012] The magnetic pallet is obtained by machining a round or squarerod or more generally a ferromagnetic slab, preferably in steel, so asto shape the base plate, the shoulder and a recess for each of themagnetic anchorage surfaces provided.

[0013] Production of a magnetic pallet from a monolithic block allowsconsiderably improved structural rigidity and stability thanks toelimination of the areas of joining between the base plate and thevertical shoulder and between the vertical shoulder and theferromagnetic crown of the magnetic anchorage surfaces of

[0014] traditional apparatus. The magnetic pallet of the presentinvention is therefore suitable for use for machining parts with highprecision.

[0015] These advantageous aspects will be made clearer by the followingdescription of a preferred embodiment of the invention, to be read byway of a non-limiting example of the more general principle claimed. Thedescription refers to the accompanying drawings in which:

[0016]FIG. 1 illustrates a front view of a magnetic pallet in accordancewith a preferred embodiment of the present invention with the magneticanchorage surface activated.

[0017]FIG. 2 shows a side elevation view of the magnetic pallet of FIG.1 partially sectioned in the condition of activation of a magneticsurface; and

[0018]FIG. 3 shows a side elevation view of the magnetic pallet of FIG.1 partially sectioned in the condition of de-activation of a magneticsurface.

[0019] Referring to the drawings, the magnetic pallet 1 for anchorage ofa ferrous part 2 to be machined by a machine tool with horizontal toolaxis comprises a base plate 3 which can be made to traverse the bed ofthe machine tool to bring the ferrous part to be machined towards thework section and to remove the machined ferrous part towards theunloading section, and a vertical shoulder 5 with a parallelepiped shapewhich extends upwards from the base plate 3. The base plate 3 and theshoulder 5 are formed in one single part by the machining of a singleferromagnetic monolithic block, preferably in steel.

[0020] At a vertical lateral face 4 of the shoulder 5 a rectangularrecess 7 of the shoulder 5 is provided, defining a back 9 and a lateralwall 11 (in addition to any vertically and horizontally extendedintermediate walls), which recess 7 serves to house a plurality ofmagnetic conductors 15 arranged in a matrix and aimed at defining avertical magnetic anchorage surface 13.

[0021] It should be noted that the recess 7 is formed by chip machiningfrom the same ferromagnetic monolithic block which forms the base plate3 and the shoulder 5 of the magnetic pallet 1.

[0022] As mentioned, in the recess of the shoulder 5 the magneticconductors 15 are fixed, which conductors have a parallelepiped shapewith horizontal axis orthogonal to the lateral face 4 of the shoulder 5,the end bases of the magnetic conductors 15 in relation to said axisbeing square in shape.

[0023] Between the internal base of each magnetic conductor 15 and theback 9 of the ferromagnetic crown 7 a primary reversible permanentmagnet 7 is interposed, having the horizontal magnetic polarisation axis(indicated by the direction of the arrow represented in the permanentmagnets 17) directed orthogonally to the internal base of the magneticconductor 15, which primary permanent magnet 17 is surrounded by anelectrical coil 19 which can be supplied with an electrical current inone direction or in the opposite direction so as to reverse thedirection (indicated by the tip of the arrow represented in the primarypermanent magnets 17) of the magnetic polarity of the primary permanentmagnet 17.

[0024] Between each of the lateral faces of each magnetic conductor 15and the opposite lateral face of the adjacent magnetic conductors 15 orthe opposite lateral wall 11 of the recess 7, if the magnetic conductor15 is peripheral in relation to the matrix arrangement of the magneticconductors 15, a secondary permanent magnet 21 is interposed. The axisof magnetic polarisation (denoted by the direction of the arrowrepresented in the permanent magnets 21) of each secondary magnet 21 isorthogonal to the lateral face of the magnetic conductors 15, while thedirection of magnetic polarisation (indicated by the tip of the arrowrepresented in the permanent magnets 21) of each secondary magnet 21 issuch that each magnetic conductor 15 is supplied laterally by magneticpoles of the same sign.

[0025] In the case of the peripheral magnetic conductors 15 in thematrix arrangement of the magnetic conductors 15, the secondarypermanent magnets 21 arranged on the peripheral sides of the magneticconductors 15 are in contact directly with the lateral wall 11 of therecess 7.

[0026] An epoxy resin 23 or another non-magnetic material is pouredinside the recess 7 to fill the gaps between the adjacent magneticconductors 15, between the magnetic conductors 15 and the lateral wall11 of the recess 7, and between the magnetic conductors 15 and the back9 of the recess 7.

[0027]25 in FIGS. 2 and 3 denotes a channel formed in the lower portionof the shoulder 5 for laying of the electrical wiring required forsupplying the coils 19 of the reversible permanent magnets 17.

[0028] In the de-activated condition of the magnetic surface 13 eachprimary permanent magnet 17 supplies the corresponding magneticconductor 15 with a magnetic pole of opposite sign to the magnetic polessupplied to the same magnetic conductor 15 by the secondary permanentmagnets 21 which surround it. In this situation the magnetic fluxgenerated by the primary permanent magnets 17 and by the secondarypermanent magnets 21 closes entirely through the recess 7 withoutinfluencing the magnetic surface 13, as illustrated by the line ofmagnetic flux indicated by a dotted line in FIG. 3. In order to do thisit is only necessary to ensure that the magnetic flux generated overallby the four secondary permanent magnets 21 of each magnetic conductor 15is equal to that generated by the primary permanent magnet 17.

[0029] In the activated condition of the magnetic surface 13 the primarypermanent magnet 17 and the secondary permanent magnets 21 surroundingeach magnetic conductor 15 supply the same pole to the magneticconductor 15. Each magnetic conductor 15 is polarised so that themagnetic anchorage surface 13 activates, defining a matrix of poleswherein each pole has laterally poles of opposite sign to its sign, anddiagonally poles of identical sign to its sign (“N” stands for northpole and “S” for south pole in FIG. 1). In this situation the magneticflux generated by the primary reversible permanent magnets 17 and by thesecondary permanent magnets 21 closes entirely through the ferrous part2 as illustrated by the lines of flux indicated by a dotted line in FIG.2.

[0030] The through section of the lateral wall and of the back of therecess 7 must be sufficient for sustaining without dispersion themagnetic flux generated by the primary and secondary magnets. In thisway, in addition to optimising the power of magnetic anchorage in theactivated condition of the magnetic anchorage surface, advantageouslythe magnetic pallet becomes completely inert in the de-activatedcondition of the magnetic anchorage surface.

[0031] It must be clear that the distribution of the polarities of thepoles of the magnetic anchorage surface can be differentiated from thatillustrated here with a different arrangement of the permanent magnetswhich generate the magnetic circuit.

[0032] For example a distribution in groups of poles of the samepolarity is possible in such a way as to vary the depth of penetrationof the magnetic field through the parts to be anchored.

[0033] Although a magnetic pallet with a single magnetic anchoragesurface has been described for the sake of simplicity, it is clear thatby the same principle a magnetic pallet can be provided which has up tofive magnetic anchorage surfaces which can be activated independently,namely one per vertical lateral face of the magnetic pallet plus one onthe upper horizontal face of the pallet.

1. A magnetic pallet (1) for the anchorage of a ferrous part to be takenfor machining by a machine tool with horizontal tool axis, said magneticpallet (1) comprising a base plate (3), a vertical parallelepipedshoulder (5) extending from the base plate (3), a first plurality ofmagnetic conductors (15) arranged in a matrix and which can be polarisedmagnetically so as to define a first magnetic anchorage surface at afirst lateral face (4) of said shoulder (5), characterised in that saidbase plate (3) and said shoulder (5) are formed from a singleferromagnetic monolithic block, and in that in said ferromagneticmonolithic block, at said first lateral face (4) of said shoulder (5), afirst recess (7) is provided for housing said first plurality ofmagnetic conductors (15).
 2. A magnetic pallet (1) according to claim 1,characterised in that it also comprises at least a second plurality ofmagnetic conductors arranged in a matrix and which can be polarisedmagnetically to define at least a second magnetic anchorage surface at asecond lateral face of said shoulder (5), at said second lateral face ofsaid shoulder (5) a second recess being formed for housing said secondplurality of magnetic conductors.
 3. A magnetic pallet (1) according toclaim 1, characterised in that said monolithic block is in ferromagneticsteel.
 4. A magnetic pallet (1) according to claim 1, characterised inthat said first plurality of magnetic conductors (15) has aparallelepiped shape with horizontal axis orthogonal to said firstlateral face (4) of said shoulder (5), and in that a first plurality ofprimary reversible permanent magnets (17) is provided, each of saidreversible permanent magnets (17) being surrounded by a correspondingelectrical induction coil (19) and being interposed between the back ofsaid recess and the axially internal base of a corresponding magneticconductor (15) of said first plurality of magnetic conductors (15), eachof said reversible permanent magnets (17) having the horizontalpolarisation axis orthogonal to said axially internal base of saidcorresponding magnetic conductor (15).
 5. Method for the production of amagnetic pallet (1) for the anchorage of a ferromagnetic part to betaken for machining to a machine tool with horizontal tool axis,characterised in that it provides the following phases of machining of aferromagnetic monolithic block: formation from said monolithic block ofa base plate (3); formation from said monolithic block of a verticalparallelepiped shoulder (5) extending from the base plate (3); andformation from said monolithic block of at least a first recess (7) forhousing a corresponding first plurality of magnetic conductors (15)arranged in a matrix and which can be polarised magnetically so as todefine a first magnetic anchorage surface at a first lateral face (4) ofsaid shoulder (5).
 6. Method for the formation of a magnetic pallet (1)according to claim 5, characterised in that it also comprises thefollowing phase: formation from said monolithic block of at least asecond recess for housing a corresponding second plurality of magneticconductors arranged in a matrix and which can be polarised magneticallyso as to define at least a second magnetic anchorage surface for ferrousparts at a second lateral face of said shoulder.
 7. A magnetic pallet(1) according to claim 2, characterised in that said monolithic block isin ferromagnetic steel.